In order to synchronize multiple displays that are connected to the same GPU the displays needs to be identical. This means they need to report the same EDID. Can you confirm that the EDID for the 3 displays that you want to synchronize are identical?

How are the Displays connected? Do you use DisplayPort to DVI adapters? If so can you confirm that you are using active adapters.

looking at the screen-shots you sent the synchronization of the displays to the house sync should be possible. When you checkmark display 3 and 4 and try to synchronize it, do you see the displays getting black? This would indicate that the driver tries to synchronize the displays.

Can you try to configure display 2 as TimingServer. In the properties of the TimingServer you can define that this display should synchronize to the house sync. Then please try to configure display 3 and 4 as Timing Client. You do not need to specify the house sync any more for the clients since they will sync to the Timing Server which is in sync with the house sync.